Our goal is to understand the mechanisms and routes of water and iron transport in epithelia specialized for fluid transport. Our approach is to apply electrophysiological techniques, such as equivalent electrical circuit analyses based on applied step pulses of current or sinusodal alternating current frequencies. The output of an epithelial membrane in response to these electrical inputs can then be modelled by an assumed, morphologically realistic equivalent electrical circuit, and circuit parameters extracted that may correspond to resistors and capacitors of actual biological membranes. Results to date indicate that these methods suffice to localize the site of the electrical resistance changes in stomach associated with onset of acid secretion; to identify these resistance changes as resulting largely from an increase in membrane area; and to obtain morphological information about membrane configuration by means of electrophysiological techniques, taking advangage of so-called distributed resistor effects.